In studying the metabolism of guanidino compounds in the human, a scheme was devised in order to explain the appearance of guanidinosuccinate or alternatively, guanidinoacetate in human urine. This scheme proposes that canaline, formed from aspartate, reacts with carbamyl phosphate to generate ureidohomoserine. Canavaninosuccinate may be reduced to form homoserine and guanidinosuccinate. This pathway is stimulated in uremia because of the impaired ability to acidify the urine. Normally, canavaninosuccinate is acted on by a lyase to form canavanine and fumarate. The canavanine transamidinates to glycine to form guanidinoacetate, regenerating canaline. All of these steps have been confirmed as taking place in human liver, in this study, except the conversion of aspartate to canaline. The mechanism of this conversion is now the subject of study in this project.